From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id D110AEE57C2 for ; Fri, 8 Sep 2023 04:44:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S239515AbjIHEoV (ORCPT ); Fri, 8 Sep 2023 00:44:21 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36808 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S239335AbjIHEoU (ORCPT ); Fri, 8 Sep 2023 00:44:20 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id ED5AB1BC1 for ; Thu, 7 Sep 2023 21:43:31 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1694148211; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=+R5PA6kHMvayYFOXlFnPP0p5Z3WLnMw7fxi33dBoYEA=; b=KBUg3unY3S/z/V3gUKOqEvwX8Fu/G2W0oiuT+l3luaGYYp7i2DDUh6chLR2U+I3TO2BwvN VLTPSvksuA0uBuN4J+BAXXC3p8P9SomDWNoQ9rUEKiN08HDz/qSrSTPD3EgNi9v8JvBf2w nKy5WTtIpG1BezfytAmrnr5BkjZ2Arw= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-637-88i7pYxnNHelyDpBFWo-ug-1; Fri, 08 Sep 2023 00:43:23 -0400 X-MC-Unique: 88i7pYxnNHelyDpBFWo-ug-1 Received: from smtp.corp.redhat.com (int-mx10.intmail.prod.int.rdu2.redhat.com [10.11.54.10]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id C85CA101CA85; Fri, 8 Sep 2023 04:43:22 +0000 (UTC) Received: from localhost (unknown [10.72.112.24]) by smtp.corp.redhat.com (Postfix) with ESMTPS id DD7DF404119; Fri, 8 Sep 2023 04:43:21 +0000 (UTC) Date: Fri, 8 Sep 2023 12:43:18 +0800 From: Baoquan He To: HAGIO =?utf-8?B?S0FaVUhJVE8o6JCp5bC+44CA5LiA5LuBKQ==?= Cc: Uladzislau Rezki , "lijiang@redhat.com" , "linux-mm@kvack.org" , Andrew Morton , LKML , Lorenzo Stoakes , Christoph Hellwig , Matthew Wilcox , "Liam R . Howlett" , Dave Chinner , "Paul E . McKenney" , Joel Fernandes , Oleksiy Avramchenko , "kexec@lists.infradead.org" Subject: Re: [PATCH v2 4/9] mm: vmalloc: Remove global vmap_area_root rb-tree Message-ID: References: <20230829081142.3619-1-urezki@gmail.com> <20230829081142.3619-5-urezki@gmail.com> <8939ea67-ca27-1aa5-dfff-37d78ad59bb8@nec.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <8939ea67-ca27-1aa5-dfff-37d78ad59bb8@nec.com> X-Scanned-By: MIMEDefang 3.1 on 10.11.54.10 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 09/08/23 at 01:51am, HAGIO KAZUHITO(萩尾 一仁) wrote: > On 2023/09/07 18:58, Baoquan He wrote: > > On 09/07/23 at 11:39am, Uladzislau Rezki wrote: > >> On Thu, Sep 07, 2023 at 10:17:39AM +0800, Baoquan He wrote: > >>> Add Kazu and Lianbo to CC, and kexec mailing list > >>> > >>> On 08/29/23 at 10:11am, Uladzislau Rezki (Sony) wrote: > >>>> Store allocated objects in a separate nodes. A va->va_start > >>>> address is converted into a correct node where it should > >>>> be placed and resided. An addr_to_node() function is used > >>>> to do a proper address conversion to determine a node that > >>>> contains a VA. > >>>> > >>>> Such approach balances VAs across nodes as a result an access > >>>> becomes scalable. Number of nodes in a system depends on number > >>>> of CPUs divided by two. The density factor in this case is 1/2. > >>>> > >>>> Please note: > >>>> > >>>> 1. As of now allocated VAs are bound to a node-0. It means the > >>>> patch does not give any difference comparing with a current > >>>> behavior; > >>>> > >>>> 2. The global vmap_area_lock, vmap_area_root are removed as there > >>>> is no need in it anymore. The vmap_area_list is still kept and > >>>> is _empty_. It is exported for a kexec only; > >>> > >>> I haven't taken a test, while accessing all nodes' busy tree to get > >>> va of the lowest address could severely impact kcore reading efficiency > >>> on system with many vmap nodes. People doing live debugging via > >>> /proc/kcore will get a little surprise. > >>> > >>> > >>> Empty vmap_area_list will break makedumpfile utility, Crash utility > >>> could be impactd too. I checked makedumpfile code, it relys on > >>> vmap_area_list to deduce the vmalloc_start value. > >>> > >> It is left part and i hope i fix it in v3. The problem here is > >> we can not give an opportunity to access to vmap internals from > >> outside. This is just not correct, i.e. you are not allowed to > >> access the list directly. > > > > Right. Thanks for the fix in v3, that is a relief of makedumpfile and > > crash. > > > > Hi Kazu, > > > > Meanwhile, I am thinking if we should evaluate the necessity of > > vmap_area_list in makedumpfile and Crash. In makedumpfile, we just use > > vmap_area_list to deduce VMALLOC_START. Wondering if we can export > > VMALLOC_START directly. Surely, the lowest va->va_start in vmap_area_list > > is a tighter low boundary of vmalloc area and can reduce unnecessary > > scanning below the lowest va. Not sure if this is the reason people > > decided to export vmap_area_list. > > The kernel commit acd99dbf5402 introduced the original vmlist entry to > vmcoreinfo, but there is no information about why it did not export > VMALLOC_START directly. > > If VMALLOC_START is exported directly to vmcoreinfo, I think it would be > enough for makedumpfile. Thanks for confirmation, Kazu. Then, below draft patch should be enough to export VMALLOC_START instead, and remove vmap_area_list. In order to get the base address of vmalloc area, constructing a vmap_area_list from multiple busy-tree seems not worth. diff --git a/Documentation/admin-guide/kdump/vmcoreinfo.rst b/Documentation/admin-guide/kdump/vmcoreinfo.rst index 599e8d3bcbc3..3cb1ea09ff26 100644 --- a/Documentation/admin-guide/kdump/vmcoreinfo.rst +++ b/Documentation/admin-guide/kdump/vmcoreinfo.rst @@ -65,11 +65,11 @@ Defines the beginning of the text section. In general, _stext indicates the kernel start address. Used to convert a virtual address from the direct kernel map to a physical address. -vmap_area_list --------------- +VMALLOC_START +------------- -Stores the virtual area list. makedumpfile gets the vmalloc start value -from this variable and its value is necessary for vmalloc translation. +Stores the base address of vmalloc area. makedumpfile gets this value and +its value is necessary for vmalloc translation. mem_map ------- diff --git a/arch/arm64/kernel/crash_core.c b/arch/arm64/kernel/crash_core.c index 66cde752cd74..2a24199a9b81 100644 --- a/arch/arm64/kernel/crash_core.c +++ b/arch/arm64/kernel/crash_core.c @@ -23,7 +23,6 @@ void arch_crash_save_vmcoreinfo(void) /* Please note VMCOREINFO_NUMBER() uses "%d", not "%x" */ vmcoreinfo_append_str("NUMBER(MODULES_VADDR)=0x%lx\n", MODULES_VADDR); vmcoreinfo_append_str("NUMBER(MODULES_END)=0x%lx\n", MODULES_END); - vmcoreinfo_append_str("NUMBER(VMALLOC_START)=0x%lx\n", VMALLOC_START); vmcoreinfo_append_str("NUMBER(VMALLOC_END)=0x%lx\n", VMALLOC_END); vmcoreinfo_append_str("NUMBER(VMEMMAP_START)=0x%lx\n", VMEMMAP_START); vmcoreinfo_append_str("NUMBER(VMEMMAP_END)=0x%lx\n", VMEMMAP_END); diff --git a/arch/riscv/kernel/crash_core.c b/arch/riscv/kernel/crash_core.c index 55f1d7856b54..5c39cedd2c5c 100644 --- a/arch/riscv/kernel/crash_core.c +++ b/arch/riscv/kernel/crash_core.c @@ -9,7 +9,6 @@ void arch_crash_save_vmcoreinfo(void) VMCOREINFO_NUMBER(phys_ram_base); vmcoreinfo_append_str("NUMBER(PAGE_OFFSET)=0x%lx\n", PAGE_OFFSET); - vmcoreinfo_append_str("NUMBER(VMALLOC_START)=0x%lx\n", VMALLOC_START); vmcoreinfo_append_str("NUMBER(VMALLOC_END)=0x%lx\n", VMALLOC_END); vmcoreinfo_append_str("NUMBER(VMEMMAP_START)=0x%lx\n", VMEMMAP_START); vmcoreinfo_append_str("NUMBER(VMEMMAP_END)=0x%lx\n", VMEMMAP_END); diff --git a/include/linux/vmalloc.h b/include/linux/vmalloc.h index c720be70c8dd..91810b4e9510 100644 --- a/include/linux/vmalloc.h +++ b/include/linux/vmalloc.h @@ -253,7 +253,6 @@ extern long vread_iter(struct iov_iter *iter, const char *addr, size_t count); /* * Internals. Don't use.. */ -extern struct list_head vmap_area_list; extern __init void vm_area_add_early(struct vm_struct *vm); extern __init void vm_area_register_early(struct vm_struct *vm, size_t align); diff --git a/kernel/crash_core.c b/kernel/crash_core.c index 03a7932cde0a..91af87930770 100644 --- a/kernel/crash_core.c +++ b/kernel/crash_core.c @@ -617,7 +617,7 @@ static int __init crash_save_vmcoreinfo_init(void) VMCOREINFO_SYMBOL_ARRAY(swapper_pg_dir); #endif VMCOREINFO_SYMBOL(_stext); - VMCOREINFO_SYMBOL(vmap_area_list); + vmcoreinfo_append_str("NUMBER(VMALLOC_START)=0x%lx\n", VMALLOC_START); #ifndef CONFIG_NUMA VMCOREINFO_SYMBOL(mem_map); diff --git a/kernel/kallsyms_selftest.c b/kernel/kallsyms_selftest.c index b4cac76ea5e9..8a689b4ff4f9 100644 --- a/kernel/kallsyms_selftest.c +++ b/kernel/kallsyms_selftest.c @@ -89,7 +89,6 @@ static struct test_item test_items[] = { ITEM_DATA(kallsyms_test_var_data_static), ITEM_DATA(kallsyms_test_var_bss), ITEM_DATA(kallsyms_test_var_data), - ITEM_DATA(vmap_area_list), #endif }; diff --git a/mm/nommu.c b/mm/nommu.c index 7f9e9e5a0e12..8c6686176ebd 100644 --- a/mm/nommu.c +++ b/mm/nommu.c @@ -131,8 +131,6 @@ int follow_pfn(struct vm_area_struct *vma, unsigned long address, } EXPORT_SYMBOL(follow_pfn); -LIST_HEAD(vmap_area_list); - void vfree(const void *addr) { kfree(addr); diff --git a/mm/vmalloc.c b/mm/vmalloc.c index 50d8239b82df..0a02633a9566 100644 --- a/mm/vmalloc.c +++ b/mm/vmalloc.c @@ -729,8 +729,7 @@ EXPORT_SYMBOL(vmalloc_to_pfn); static DEFINE_SPINLOCK(free_vmap_area_lock); -/* Export for kexec only */ -LIST_HEAD(vmap_area_list); + static bool vmap_initialized __read_mostly; /* -- 2.41.0